Since long biocompatible materials have beers applied in augmenting soft tissue in the practice of plastic and reconstructive surgery. These biomaterials are commonly delivered to the tissue site where augmentation is desired by means of an injectable composition that comprises biomaterial and a biocompatible fluid, wherein the fluid acts as a lubricant to improve the delivery of the biomaterial suspension.
Since the mid-eighties polymethylmethacrylate (PMMA) has been studied as a soft tissue augmentation device, replacing then popular collagen. The permanent character of PMMA and many other fillers such as silicones would make repetitious corrections unnecessary. However, it is discovered recently that the injection of PMMA microspheres causes all kinds of complications in time, to a large extent related to the non-biodegradable properties. Moreover, it is now believed that the permanent impact of filler materials in tissue is undesired, since the tissue itself is subject to ageing (see e.g. E. Haneke, “Skin rejuvenation without a scalpel I. Fillers”, J Cosmetic Dermatology; 5; 15-167 (2005): K. De Boulle, “Management of complications after impantation of fillers”, J Cosmetic Dermatology; 3:2-15 (2004).
WO-A-93/16657 teaches the use of injectable ceramic compositions comprising biocompatible ceramic materials such as calcium hydroxyapatite in a fluid carrier. These ceramics show excellent performance in repair and augmentation of soft and hard tissues. Further, hydroxyapatite has very low immunogenicity. The 50-250 μm sized ceramic particles are stabilized in a viscous or even gel-like organic polymer, such as polyethylene glycol, hyaluronic acid, poly(hydroxyethyl methacrylate), or in a collagen hydrogel.
Of about the same time, WO-A-93/15721 discloses a matrix of smooth, rounded, substantially spherical, finely divided particles of calcium hydroxyapatite in a biocompatible, resorbable lubricious gel carrier comprising a polysaccharide. The particles are typically in the range of 35-150 μm to minimize the possibility of particle migration by phagocytosis and to facilitate injectability. The carrier serves to further improve the delivery of the augmentation material by injection to the tissue site where augmentation is desired, and is typically formed from water, about 25 wt % glycerin and sodium carboxymethyl cellulose. It enables the ceramic particles to remain in suspension without settling for an indefinite period of time until used, more specifically at least about 6 months. U.S. Pat. No. 4,803,075 suggests the use of further biocompatible fluid lubricants and/or viscosity modifiers, such as glycogen, maltose and the like.
However, the use of foreign body carrier materials renders these injectable hydroxyapatite compositions unattractive. In the art there is a continuous need to improve biocompatible implant materials tor soil and hard tissue repair and augmentation, wherein the use of foreign body materials is minimised or even avoided. The ideal soft tissue filler would be non-permanent biocompatible, have minimal side effects, not require allergy testing, be easy to use/inject, be painless to inject, and be cost-effective for both the physician and the patient.